Alkyd resins are polyester resins derived from the reaction of polyols with dicarboxylic acids or anhydrides, and modified by fatty acids. Conventional methods for making alkyd resins use fatty acids derived from vegetable oils, tall oils, short oils, and the like. Although alkyd resins are typically solvent-based, environmental concerns over volatile organic compound (VOC) content in coating compositions has led to interest in water-reducible or water-dispersible alkyd resins.
Environmental concerns over increasing quantities of waste or post-consumer materials have created interest in coating compositions made from waste materials. For example, fast food restaurants generate large quantities of used vegetable oil or waste oil. The waste cooking oil can pose a pollution hazard and has the potential to clog waterways and drain systems during disposal. Therefore, used cooking oil, called yellow grease or brown grease, is typically trapped and filtered out of waste water streams and rendered into animal feed, biodiesel fuel and the like. In addition, waste cooking oil may be used as a fatty acid feedstock for producing alkyd resins, although these alkyd resins may lack the hardness, durability and early water resistance required of a water-reducible coating composition.
Other waste or post-consumer materials may also be used as feedstock for making alkyd resins. For example, polyethylene terephthalate is in widespread use, and recycling PET helps manage solid waste problems while conserving resources and energy. However, water-reducible resins with high PET content typically demonstrate poor water resistance and may not be useful in making corrosion-resistant coating compositions.
Therefore, in view of the foregoing, increasing environmental concerns may be met by new water-reducible or water-dispersible coatings derived from waste or post-consumer materials, where the coatings demonstrate optimal durability, water resistance and corrosion resistance.